from Wiktionary, Creative Commons Attribution/Share-Alike License
- n. A rare silicate mineral of the mica group.
from The Century Dictionary and Cyclopedia
- n. In mineralogy, a kind of mica, allied to biotite, but characterized by the presence of a large amount of iron protoxid and the almost complete absence of magnesia: it is found near Pike's Peak in Colorado.
sidero- + phyllite (Wiktionary)